Microsoft Word C032824e doc Reference number ISO 8178 10 2002(E) © ISO 2002 INTERNATIONAL STANDARD ISO 8178 10 First edition 2002 11 01 Reciprocating internal combustion engines — Exhaust emission mea[.]
Ambient test conditions
To ensure accurate engine performance assessments, the absolute temperature of the intake air (Tₐ) in Kelvin and the dry atmospheric pressure (pₛ) in kilopascals must be precisely measured The parameter, fₐ, should then be calculated following the guidelines and evaluated using equations (3) to (5).
Naturally-aspirated and mechanically-supercharged compression ignition engines, and compression ignition engines with wastegates operating:
This equation remains applicable even if the wastegate operates only during specific parts of the test cycle If the wastegate is inactive during the entire test cycle, equations (4) or (5) should be used, depending on the type of charge cooling employed.
Turbocharged compression ignition engines without charge air cooling, or with charge air cooling by air/air cooler:
Turbocharged compression ignition engines with charge air to liquid charge air cooler:
5.1.2 Test validation criteria — Test conditions
For a test to be recognized as valid, with respect to atmospheric conditions, the parameter f a should be such that:
Smoke values obtained within this range of f a shall be corrected in accordance with the provisions given in 10.3
Results from tests conducted outside this range are not comparable to the results from ISO 8178-9
Additional validation criteria are given in 7.3.4 (opacimeter zero drift) and annexes A to C (test cycle validation criteria).
Power
Auxiliaries necessary solely for machine operation must be turned off; if they cannot be switched off, they should operate at minimal power during testing Ensuring auxiliary systems are minimized or deactivated enhances safety and accuracy during machinery assessments Examples include specific auxiliary systems that support machine function but are not vital for the test, which should be managed accordingly to comply with safety standards Proper control of auxiliaries helps prevent unintended operation and maintains optimal testing conditions.
auxiliary electrical equipment (lights, blowers, etc.).
Engine air inlet system
Regular inspection of the inlet air system is essential to identify leaks, loose clamps, or missing fittings, ensuring optimal performance The overall condition of the air system should be assessed, including checking if the air cleaner requires servicing, to maintain efficient operation and prevent potential issues.
Engine exhaust system
The exhaust system shall be inspected for leaks, loose or missing clamps or fittings, etc The general condition of the exhaust system shall be noted.
Engines with charge air cooling
The charge air cooling system shall be inspected for leaks, loose or missing clamps or fittings, etc The general condition of the charge air cooling system shall be noted
Fuel characteristics significantly impact engine smoke emissions, with ISO 8178-9-compliant tests serving as certification or type approval procedures that use specified reference fuels Field tests are usually conducted with different fuels, making it essential to determine, record, and present the fuel characteristics used during testing—especially for vehicles failing the smoke test—to ensure accurate interpretation of results and compliance.
When using fuels designated as reference fuels in ISO 8178-5, the reference code and detailed fuel analysis must be provided For all other fuels, their characteristics should be documented according to the parameters specified in the relevant universal data sheets within ISO 8178-5, ensuring accurate and standardized reporting.
The choice of fuel for testing is determined by the specific objectives of the test Typically, unless otherwise agreed upon by the parties involved, the fuel used should conform to the specifications outlined in Table 2 This ensures consistency and reliability in test results while adhering to industry standards.
Table 2 — Selection of fuel Test purpose Interested parties Fuel selection
Reference fuel, if one is defined
Commercial fuel if no reference fuel is defined
Inspection/maintenance test Manufacturer or supplier
Commercial fuel as specified by the manufacturer a
One or more of: manufacturer, research organization, fuel and lubricant supplier, etc
Customers and inspectors should be aware that emission tests conducted using commercial fuel may not produce results comparable to those obtained with reference fuels, depending on the testing purpose.
For acceptance testing, the fuel must meet the specifications outlined in the engine manufacturer's technical literature If the designated reference fuel is unavailable, a substitute with closely matching properties can be used, provided its characteristics are clearly declared.
General
The equipment mentioned in 7.3 shall be used for smoke tests of engines in the field.
Test conditions
This part of ISO 8178 does not contain details of engine speed, pressure and temperature measuring equipment
Instead, only the accuracy requirements of such equipment are given in 7.4
Accurate measurement of engine speed is essential to ensure that tests are conducted correctly and that the engine governor functions properly, preventing potential engine damage Maintaining the correct idle speed is crucial, as incorrect low or high RPMs can affect emissions results and cause deviations from the standards outlined in ISO 8178-9 Monitoring engine speed helps achieve reliable test outcomes and adherence to regulatory requirements.
Ambient temperature (dry bulb temperature) is essential for accurately correcting smoke emissions during ambient testing, ensuring that measurements reflect true engine performance under test conditions This information is crucial for determining whether the engine complies with the certification standards, as specified by relevant regulations and standards Proper measurement of ambient temperature allows for standardized assessment and verification of engine emissions, ensuring compliance and environmental safety.
Dry ambient pressure is essential for accurate smoke correction and assessing engine compliance with ISO 8178-9 standards It is calculated by subtracting vapor pressure—determined from dew point or wet and dry bulb temperature measurements—from the measured wet ambient (barometric) pressure Proper evaluation of dry ambient pressure ensures precise emission testing and adherence to regulatory requirements.
Determination of smoke
Transient smoke tests must be performed using opacimeter-type smokemeters, with three authorized types: in-line full flow, end-of-line full flow, and partial flow opacimeters Detailed specifications for these opacimeter types are outlined in clause 11 of ISO 8178, as well as in clauses 6 and 7 of the relevant standard Ensuring the use of compliant smokemeters is essential for accurate transient smoke testing and maintaining standards compliance.
ISO 11614:1999 Temperature correction has not been validated for transient tests, therefore, temperature correction of smoke results has not been included in this part of ISO 8178
Smoke tests necessitate a comprehensive smoke measurement and data processing system comprising three essential functional units These units can be integrated into a single component or operate as an interconnected system, ensuring accurate smoke detection, measurement, and data analysis Proper implementation of these units is critical for reliable smoke testing and environmental monitoring.
a full-flow or a partial-flow opacimeter meeting the specifications of this clause Detailed specifications for opacimeters can be found in clause 11 and in ISO 11614;
a data processing unit capable of performing the functions described in 10.2 and 10.3 and in the applicable annex (A, B or C);
a printer and/or electronic storage medium to record and output the required smoke values specified in the applicable annex (A, B or C)
The linearity is the difference between the value measured by the opacimeter and the reference value of the calibrating device The linearity shall not exceed ± 2 % opacity
The zero drift during the lesser of a one hour period or the duration of the test shall not exceed ± 0,5 % opacity or
2 % of full scale, whichever is smaller
The opacimeter must have a measuring range suitable for accurately assessing the smoke emitted by the engine under test, ensuring reliable readings of both opacity and light absorption coefficient Additionally, it should offer a minimum resolution of 0.1% of the full scale to provide precise and consistent measurements.
The optical path length selected for the smoke instrument shall be suitable for the smoke levels being measured, in order to minimize errors in calibrations, measurements and calculations
The physical response time of the opacimeter shall not exceed 0,2 s, and the electrical response time of the opacimeter shall not exceed 0,05 s
7.3.7 Sampling requirements for partial flow opacimeters
The sampling conditions shall conform to the requirements of 11.3 of ISO 8178-9:2000
The light source shall conform to the requirements of 11.2 and 11.3 of ISO 8178-9:2000
Neutral density filters used for calibrating and verifying opacimeters must have an opacity accuracy within ±1% Their nominal values should be checked annually against a reference traceable to national or international standards to ensure measurement precision and compliance.
Neutral density filters are delicate precision devices that can be easily damaged if mishandled To ensure their longevity, handling should be minimized and done with utmost care to prevent scratches, dirt, or other damage Proper maintenance and cautious use are essential for preserving the filter’s effectiveness and clarity.
Accuracy
The calibration of all measuring instruments shall be traceable to international (national if no international standards exist) standards and comply with the requirements given in Table 3
Table 3 — Permissible deviations of instruments for engine-related parameters
Item Permissible deviation Calibration intervals months
ISO 8178-1 specifies the measurement of intake air temperature, while ISO 8178 uses ambient temperature, which can vary significantly depending on engine installations It is important to account for the differences between intake air temperature and ambient temperature, especially in setups where the disparity may be substantial Accurate measurement of these temperatures ensures compliance with ISO standards and optimal engine performance.
General
The opacimeter shall be calibrated as often as necessary to fulfill the accuracy requirements of this part of
ISO 8178 The calibration method that shall be used is described in 8.2.
Calibration procedure
Ensure the opacimeter is properly warmed up and stabilized following the manufacturer's instructions for optimal accuracy If equipped with a purge air system to prevent sooting of the optics, activate and adjust it according to the manufacturer's guidelines.
8.2.2 Establishment of the linearity response
With the opacimeter in the opacity readout mode, and with no blockage of the opacimeter light beam, the readout shall be adjusted to 0,0 % ± 0,5 % opacity
With the opacimeter in the opacity readout mode, and all light prevented from reaching the receiver, the readout shall be adjusted to 100,0 % ± 0,5 % opacity
To ensure accurate measurements, the opacimeter’s linearity in opacity mode must be checked regularly according to the manufacturer’s recommendations This involves introducing a neutral density filter between 30% and 60% full scale that complies with specified requirements, and recording the measurement value The instrument’s readout should not differ by more than ±2% opacity from the filter’s nominal value Any non-linearity exceeding this threshold must be corrected before conducting tests to guarantee reliable results.
Installation of the measuring equipment
The opacimeter and sample probes should be installed after the muffler or any after-treatment device, following the manufacturer’s installation instructions For accurate smoke measurement, it is essential to perform testing before ambient air enters the exhaust pipe and mixes with the exhaust stream, especially when comparing results to ISO 8178-9 standards.
When using a full-flow end-of-line smokemeter, it is essential to observe the requirements of clause 10 of ISO 11614:1999, where applicable The parameter L A depends on the vehicle's exhaust system and the mounting position of the smokemeter on the tailpipe Accurate determination of L A for different exhaust pipe types is detailed in section 9.2 Limited accessibility to the exhaust system in some machinery may prevent proper installation, potentially affecting the comparability of smoke test results with ISO 8178-9 standards. -**Sponsor**Need help making your article shine and comply with SEO rules? It sounds like you're looking for a way to distill the core meaning of your paragraphs With [Article Generation](https://pollinations.ai/redirect-nexad/3WncdnXT), you can instantly create SEO-optimized articles, even from complex source material like technical standards Imagine getting perfectly rewritten, 2,000-word articles in a snap! You'll save time and potentially over $2,500 a month compared to hiring a writer, all while ensuring your content is clear, concise, and SEO-friendly.
Excessively windy conditions should be avoided to ensure accurate smoke measurements Winds are deemed excessive if they disrupt the size, shape, or position of the smoke plume in the sampling or measurement area To mitigate wind effects, locate the machinery in a wind-sheltered location or utilize specialized measuring equipment designed to minimize wind interference during sampling and measurements.
Ensure that no visible humidity, such as rain, fog, or snow, is present in the area where exhaust samples are collected or smoke plumes are measured, to guarantee accurate readings Take precautions to prevent direct sunlight from shining on the smoke plume or measurement receiver, as sunlight can affect measurement accuracy Some equipment designs are specifically engineered to mitigate the impact of environmental conditions like humidity and sunlight, ensuring reliable emission testing results Complying with these conditions is essential for precise and consistent exhaust emission measurements.
Determination of effective optical path length (L A )
To ensure accurate smoke measurement, only portions of the light path that pass through smoke-obscured areas contribute to the effective optical path length; sections not obscured by smoke do not influence the measurement When the smokemeter light beam is positioned within 0.07 meters of the exhaust outlet, the cross-section of the passing smoke plume closely matches the tailpipe outlet, facilitating precise readings Accurate determination of the tailpipe outlet distance, preferably through direct measurement, is essential for correct smoke opacity results To achieve measurements within ±2% opacity, the optical path length (L A) must be determined within ±6%, with the largest errors typically occurring at around 60% opacity; at lower or higher opacity levels, slightly less precise measurements are acceptable For the standard effective optical path length of 0.038 meters, a ±6% accuracy corresponds to approximately 0.002 meters in measurement precision.
Accessing and obtaining direct measurements of tailpipe outlets during field testing can be challenging on many machines To address this, extending the exhaust stack pipe from three to a maximum of thirty times the stack diameter is recommended, provided the engine manufacturer has no objections Ensuring a proper seal at the joint is essential to prevent exhaust dilution with air.
Accurately determining the length of the tailpipe (L A) can often be achieved by analyzing external exhaust system dimensions, which are easier to measure This section outlines the specific cases where this method applies, along with the fundamental principles and procedures to reliably determine L A for various tailpipe designs.
9.2.2 External versus internal tailpipe dimensions
Most tailpipes encountered on machines are constructed from metal tubing of various standard nominal sizes
Nominal tubing sizes are based on the tubing OD whereas it is the internal dimension of the tailpipe that dictates
L A The difference between the external and internal tailpipe dimension is twice the tubing wall thickness, which is typically small
Using the external tailpipe dimension as the measured effective optical path length can lead to slightly underestimated corrected smoke values, typically less than 1% opacity, which is acceptable in most cases However, for applications requiring high precision or when the tailpipe wall thickness is unusually substantial, it is important to account for the material thickness in calculating the optical path length (L A) to ensure accurate smoke measurement results.
9.2.2.2 Straight circular non-bevelled tailpipes
The simplest tailpipe design, as shown in Figure 1, involves positioning the smokemeter light beam perpendicular to and passing through the center of the smoke plume, within 0.05 meters of the tailpipe exit Following these guidelines ensures accurate measurement, with L A typically equal to the tailpipe inner diameter (ID) and often approximated by the outer diameter (OD), as outlined in section 9.2.2.1.
2 Circular tailpipe a Exhaust flow b L A∞ = Tailpipe inner diameter; L A∞ = Tailpipe outer diameter for wall thickness less than 1,5 mm c u 5 cm
Figure 1 — Straight circular non-bevelled tailpipe
A bevelled tailpipe occurs when the outlet is not cut perpendicular to the exhaust flow axis For such tailpipes, the recommended smokemeter mounting orientation requires the light beam to be perpendicular to and passing through the central axis of the smoke plume, parallel to the minor axis of its elliptical shape The smokemeter light must also be within 0.05 meters of the tailpipe outlet to ensure accurate measurements When these guidelines are followed, the distance LA equals the tailpipe inner diameter (ID) and can often be approximated by the tailpipe outer diameter (OD), facilitating precise smokemeter positioning and emission testing.
A full flow smokemeter is designed to measure exhaust emissions accurately, with key specifications including the inner diameter (A) and outer diameter (L A) of the tailpipe, especially when the wall thickness is less than 1.5 mm Proper placement is crucial; the light beam should be perpendicular to the exhaust flow to ensure precise readings Typically, the "A" dimension should be greater than 50 mm for optimal operation Additionally, certain smokemeter orientations, such as those involving straight circular or beveled tailpipes, are not recommended to maintain measurement accuracy Properly configured, as shown in Figure 2 with straight circular bevelled tailpipes, ensures reliable emission testing results.
When the central axis of the tailpipe is curved near the exit, the tailpipe is considered curved and its outlet cross section is non-circular To ensure accurate readings, the smokemeter should be positioned so that the light beam is perpendicular to and passes through the central axis of the smoke plume, aligned parallel to the tailpipe's minor axis, and within 0.05 meters of the tailpipe exit Following these guidelines, the effective length (L A) can be approximated as the tailpipe inner diameter (ID), usually close to the outer diameter (OD) If the smokemeter is oriented differently, L A must be measured directly to maintain measurement accuracy.
The full flow smokemeter features a 5 cm measurement and includes key specifications such as the minor axis of the outlet, which corresponds to the tailpipe's inner diameter; the tailpipe outer diameter, appropriate for wall thicknesses less than 1.5 mm; and the major axis of the outlet, which exceeds the tailpipe's inner diameter and must be determined through direct measurement.
For non-circular tailpipe cross sections, the smokemeter must be properly positioned so that its light beam is perpendicular to and passes through the central axis of the smoke plume Additionally, the smokemeter should be mounted within 0.05 meters of the tailpipe exit to ensure accurate emissions testing Proper alignment of the smokemeter is essential for reliable smoke measurement and compliance with emission standards.
For accurate measurement of L A, it should be determined directly, especially when the tailpipe has an oval or elliptical cross section Aligning the smokemeter light beam with either the major or minor axis of the tailpipe enhances measurement accuracy (see Figure 4) The recommended smokemeter orientation ensures precise readings, whereas improper alignment is not advised for reliable results.
1 Full flow smokemeter a u 5 cm b L A = Minor axis to be determined by direct measurement c L A = Major axis to be determined by direct measurement d L A = Major or minor axis difficult to measure
Smoke measurements cannot be conducted using a full-flow end-of-line smokemeter if a tailpipe rain cap is in place To ensure accurate testing, rain caps should be removed or fully secured in the open position before performing smoke tests If the rain cap remains during testing, the smokemeter must be properly oriented to prevent interference with the smoke plume or obstruction of the light beam, ensuring reliable measurement results.
2 Raincap secured in fully open position; smokemeter oriented so that the light beam is not interrupted by open rain cap a u 5 cm
Many machines feature horizontal exhaust systems mounted beneath the chassis, equipped with curved tailpipes that direct exhaust flow downward toward the ground surface This design ensures effective emission dispersion while protecting surrounding components Properly positioned exhaust systems enhance machine safety, reduce emissions impact, and improve overall performance in various working environments.
When using a full-flow end-of-line smokemeter with machines equipped with certain exhaust systems, caution is essential, as exhaust gases may rebound off the ground and recirculate through the smokemeter’s light beam This recirculation can lead to falsely elevated smoke readings, especially if dust particles become entrained in the recirculating exhaust flow Proper setup and monitoring are crucial to ensure accurate emissions measurements.
Preventing recirculation during testing is often challenging, but testing personnel should monitor for signs of recirculation when using machines with downward-directed exhaust systems If recirculation impacts smoke measurement results, the test data may be unreliable and tend to be artificially high Therefore, it is essential to interpret such results with caution to ensure accurate assessment of test outcomes.
Checking of the opacimeter
Before conducting zero and full-scale checks, the opacimeter must be properly warmed up and stabilized following the manufacturer’s instructions If equipped with a purge air system to prevent sooting of the optics, it should be activated and adjusted according to the manufacturer’s recommendations to ensure accurate measurements.
Zero and full-scale checks must be performed during the opacity readout to ensure accurate measurements The light absorption coefficient is correctly calculated using the measured opacity and the L A value provided by the opacimeter manufacturer This process is essential when switching the instrument back to the k readout mode for testing, ensuring reliable and precise results.
To ensure accurate opacity measurement, the opacimeter must be calibrated correctly When the light beam is unobstructed, the readout should be adjusted to 0.0% ± 0.5% opacity, indicating no opacity Conversely, when the light is blocked from reaching the receiver, the readout should be set to 100.0% ± 0.5% opacity, representing maximum opacity Proper calibration with these reference points guarantees precise and reliable measurements.
Test cycle
The engine shall be run on the test cycle as described in the applicable annexes A, B and C taking into account the considerations noted in annex D
NOTE Test cycles for constant-speed off-road engines are given in ISO 8178-9
Before conducting the test, ensure the transmission is correctly positioned—manual transmissions in neutral with the clutch released, and automatic transmissions in park or neutral The machine must be securely restrained to prevent movement during testing Turn off the air conditioning and deactivate any engine brakes to ensure accurate results All auxiliary devices, such as lights and accessories that could affect engine performance, should be turned off Additionally, all implements and attachments must be positioned safely and restrained if needed to prevent movement Proper preparation ensures safety and accuracy during testing.
Data evaluation
Smoke shall be sampled at a minimum frequency of 20 Hz to ensure accurate measurement Correctments for opacimeter optical path length differences, smoke units, and ambient test conditions must be applied as specified in sections 10.1.2, 10.1.3, 10.1.4, and 10.3 to obtain reliable data The processed smoke data shall then be analyzed using the Bessel algorithm, as outlined in the relevant guidelines.
According to section 10.3, sample line length does not influence the shape of the smoke trace, ensuring measurement accuracy However, longer sample lines can cause delays between smoke production and measurement, which must be considered during analysis To ensure precise results, the analysis of smoke traces should account for any transport delays within the exhaust system.
The smoke values shall then be calculated as described in the applicable annex
The Beer-Lambert law defines the relationship between transmittance, light absorption coefficient and effective optical path length as shown in equation (7)
From the definitions of transmittance and opacity, the relationship between these parameters may be defined as shown in equation (8)
From equations (7) and (8) the following relationships are derived:
Converting as-measured smoke values to appropriate reporting units involves a two-step process The first step is to convert transmittance (τ) to opacity at the effective optical path length (N_A) using a specific equation Most opacimeters perform this conversion internally, rendering the process transparent to users, thereby ensuring accurate and consistent smoke measurement reporting.
The second step of the process is to convert from N A to the desired reporting units as follows
When reporting test results in opacity units, it is essential to convert the measured opacity at the as-measured effective optical path length (NA) to the standard effective optical path length (NAS) This conversion is performed using Equation (9), ensuring consistent and accurate comparison of opacity values across different measurements and standards.
NOTE In the event that the measured and standard effective optical path lengths are identical, N AS is equal to N A and this secondary conversion step is not required
If the test results are reported in units of light absorption coefficient, then equation (10) shall be applied
10.1.4 Effective optical path length input values
To apply equation (10), it is essential to input the measured effective optical path length, L_A For using equation (9), both the measured effective optical path length, L_A, and the standard effective optical path length, L_AS, must be provided This ensures accurate calculations and proper application of the equations in optical analysis.
For full-flow end-of-line opacimeters, L A is a function of the engine tailpipe design (see 9.2)
For partial flow (sampling) and full-flow in-line opacimeters, the parameter L_A is a fixed function determined by the instrument’s measurement cell and purge air system design Accurate L_A values should be obtained using specification data provided by the manufacturer, ensuring proper operation and compliance with performance standards.
It may be necessary to determine L A within 0,002 m to achieve corrected smoke results that are accurate to within ± 2 % opacity (see 9.2)
Smoke opacity readings are influenced by the optical path length of the instrument, with limit values typically expressed in percent opacity based on standard effective path lengths, which correspond to the pipe diameter To ensure accurate data comparison, smoke opacity results should be reported at these standardized optical path lengths, denoted as L_AS in Table 4 Although measurements can be taken at non-standard optical path lengths, the engine power does not need to be recorded for the purposes of this standard.
Engine power is usually listed on a label on the engine, detailed in the owner's manual, or obtained from certification or type approval documentation If engine power cannot be determined, assessing the engine’s compliance with opacity limit values becomes impossible.
Table 4 — Standard effective optical path lengths
Standard effective optical path length
Bessel algorithm
The Bessel algorithm is used to accurately compute average smoke levels from instantaneous readings, typically applied to light absorption coefficients When smoke opacity is below 40%, the algorithm can also be used with minimal error on the opacity signal This algorithm functions as a low-pass second-order filter, requiring iterative calculations to determine its coefficients, which depend on the system's response time and sampling rate for precise results.
Therefore, 10.2.2 shall be repeated whenever the system response time and/or sampling rate changes
10.2.2 Calculation of filter response time and Bessel constants
The Bessel filter response time, t_F, is determined by the combined physical and electrical response times of the opacimeter system, as outlined in section 3.7.3 It also depends on the targeted overall response time, denoted as X To calculate t_F, the specific equation (11) must be used, ensuring accurate filtering based on system performance requirements Proper understanding and application of this calculation are essential for optimal system response and measurement accuracy.
F p e t = X − t + t (11) where: t p is the physical response time in seconds; t e is the electrical response time in seconds
The equation allows for adjusting different opacimeters to a common response time, provided that both t p and t e are significantly less than X (refer to 7.3.6) Additionally, this adjustment is valid only when both t p and t e are much shorter than the duration of the transient test, ensuring accurate comparisons and consistent measurement standards.
The calculations for estimating the filter cutoff frequency, f c , are based on a step input of 0 to 1 in < 0,01 s
The response time is defined as the duration between when the Bessel output reaches 10% (t₁₀) and 90% (t₉₀) of the step function, ensuring accurate measurement of system dynamics To determine this, iterative adjustments are made to the cutoff frequency (f_c) until the difference (t₉₀ – t₁₀) closely approximates the desired response time (t_F) The initial estimate for f_c is calculated using equation (12), providing a starting point for the iterative process Optimizing f_c through this method allows for precise control over the response characteristics in signal processing systems.
The Bessel constants E and K shall be calculated by equations (13) and (14):
Using the values of E and K, the Bessel-averaged response to a step input S i shall be calculated as follows:
The response time, tF, for a specific cutoff frequency, fc, is determined by interpolating between the times t10 and t90, which represent key points on the system's response The difference between t90 and t10 defines the response time, providing an accurate measure of system performance If the calculated response time does not closely match the desired response time, the process is iterated until the actual response time is within 1% of the specified requirement, ensuring precise and reliable results.
The Bessel algorithm is a new procedure introduced for smoke determination filtering An explanation of the Bessel filter, along with an example of its design and calculation of final smoke values, is provided in annex D of ISO 8178-9:2000 The Bessel algorithm constants depend solely on the opacimeter design and the data acquisition sampling rate It is recommended that opacimeter manufacturers supply specific filter constants for various sampling rates, enabling users to accurately design the Bessel algorithm and calculate precise smoke values.
10.2.3 Calculation of Bessel averaged smoke
Once the proper Bessel algorithm constants E and K have been calculated in accordance with 10.2.2, the Bessel algorithm shall then be applied to the instantaneous smoke trace using equation (15)
The Bessel algorithm is inherently recursive, requiring initial input values of Si−1 and Si−2, along with initial output values Yi−1 and Yi−2, to initiate the process These initial values are typically assumed to be zero, enabling the algorithm to commence effectively Proper initialization is essential for accurate and efficient execution of the Bessel algorithm in signal processing applications.
The resultant Bessel-averaged smoke values are then used to calculate the appropriate smoke values as described in the appropriate annex.
Ambient correction
Engine smoke measurements must be corrected for ambient conditions when comparing in-use smoke values to regulated limit levels If the f_a value falls within the range of 0.93 to 1.07, smoke correction should be performed using equation (19) However, the validity of this correction method has not been confirmed outside this range, and while measurements outside 0.93 to 1.07 can be adjusted with equation (19), such results should not be compared to ISO 8178-9 standards.
The air density correction equations provided are based on the best-fit nominal sensitivity derived from a sample of engines and vehicles However, individual engines exhibit varying sensitivity levels to air density changes, with some being more sensitive and others less so than predicted Consequently, applying these correction equations to specific vehicles with unknown air density sensitivity offers only approximate adjustments It is advisable for regulatory agencies to account for this variability when implementing such procedures, recognizing that the actual sensitivity of tested vehicles may differ from the nominal values.
The correction factor given in 10.3.3 accounts for engine intake dry air density The reference dry air density is
1,157 5 kg/m 3 at the reference temperature of 298 K and the reference pressure of 99 kPa (see 5.1.1)
To ensure accurate measurement, corrections should be applied to smoke values expressed as the light absorption coefficient (k), specifically to the Bessel-averaged peak smoke values rather than the raw smoke trace Opacity measurements need to be converted to the absorption coefficient using equation (10), allowing for proper correction application After correction, the values can be reconverted back to opacity units, maintaining consistency with standard measurement protocols.
Using equation (17), smoke values in the annexes shall be corrected from “observed” to “corrected” values of light absorption coefficient as follows: corr s obs k = K × k (19)
Test report
The test report shall contain the data specified in ISO 8178-6
11.2 and 11.3 of ISO 8178-9:2000 contain detailed descriptions of the recommended opacimeter systems Since various configurations can produce equivalent results, exact conformance with the figures is not required
Additional components like instruments, valves, solenoids, pumps, and switches are essential for providing supplementary information and coordinating the functions of component systems Carefully selecting or excluding non-critical components based on sound engineering judgment can optimize system performance without compromising accuracy.
The measurement principle involves transmitting light through a specific length of smoke and assessing the proportion of incident light that reaches the receiver to determine the medium's light obscuration properties Smoke measurement methods vary based on the apparatus design, including full-flow in-line opacimeters placed within the exhaust pipe, full-flow end-of-line opacimeters positioned at the exhaust pipe’s exit, or partial-flow opacimeters sampling smoke from the exhaust To accurately determine the light absorption coefficient from the opacity signal, the optical path length must be provided by the instrument manufacturer, ensuring measurement consistency and reliability.
Test cycle for variable-speed off-road engines
The smoke cycle outlined in this annex involves an acceleration from low to high idle, specifically designed for variable speed engines included in the C1 cycle of ISO 8178-4:1996 This transient smoke cycle serves as a straightforward in-use emission test that can be easily performed on diesel engines installed in various machines.
The C1 category of ISO 8178-4:1996 is for “Off-road vehicles, diesel powered off-road industrial equipment”
Typical applications for C1 engines included in the scope of this annex include, but are not limited to,
industrial drilling rigs, compressors etc.;
construction equipment including wheel loaders, bulldozers, crawler tractors, crawler loaders;
truck-type loaders, off-highway trucks, hydraulic excavators etc.;
self propelled agricultural vehicles (including tractors);
road maintenance equipment (motor graders, road rollers, asphalt finishers);
The transient smoke test outlined in this annex may not be applicable to all engines or machines due to varying control strategies Certain engine and machine control systems can restrict acceleration from slow idle to high idle, potentially preventing the test from being performed effectively.
Smoke measurement for one- or two-cylinder engines can be affected by pulsations, making reliable readings difficult without a damping volume such as a muffler To ensure accurate results, it is recommended to use a muffler or similar damping device during testing For specialized applications, custom test procedures may be implemented if mutually agreed upon by all parties involved Proper measurement techniques are essential for compliance and precision in engine emissions testing.
A.2.1 acceleration test test consisting of accelerating the engine against its own internal inertia, flywheel and unloaded machine parasitics from low idle speed to high idle speed
FAT time, in seconds, required for the engine to go from 5 % above low idle speed to 95 % of rated speed in the free acceleration test
For this field test procedure, FAT (Fire Acceptance Time) can be estimated as the time it takes for the engine to accelerate from low idle to high idle speed, with a recommended approximate value established during the in-field smoke test Unusually high rotating inertias or significant parasitic loads may cause the in-use FAT to exceed 9 FAT as defined by ISO 8178-9:2000 annex A, and in such cases, in-use smoke measurements should not be directly compared to the standard limit values, since the test conditions may fall outside the certified or type-approved parameters of the engine.
PSV s highest 1,0 second Bessel-averaged smoke value obtained during the acceleration in A.3.5.1 e) for the in-service test (s = service)
NOTE The reported value for PSV s is the average of the three individual accelerations of A.3.5.1 e)
The test consists of engine accelerations between low idle speeds and high idle speeds Multiple accelerations are conducted to reduce variability
Ensure the engine is turned off, the parking brake is engaged, and all implements and attachments are securely positioned according to safety standards During inspection, check for loose or missing parts, with special attention to the intake and exhaust systems, and examine the fuel system for signs of tampering or damage Proper maintenance and prevention of tampering are crucial to prevent engine failure during smoke testing Additionally, record essential engine details such as engine power, model type, serial number, and engine family as part of the comprehensive inspection process.
Low idle speed shall be checked and recorded prior to running a smoke test
Before performing the smoke test, it is essential to check the high idle speed to prevent engine damage Gradually move the speed control to full speed while monitoring the engine RPM If the engine exceeds the manufacturer’s recommended high idle speed, immediately revert the control to low idle and discontinue the smoke test to ensure engine safety.
The engine shall be warmed up by operating it at least 15 min under load Alternatively, oil and coolant temperature gauges may be used to confirm that the engine is at normal operating temperatures
NOTE A preconditioning phase should also protect the actual measurement against the influence of deposits in the exhaust system from a former test
Ensure the parking brake is engaged and all implements and attachments are securely in a safe position before operation Turn off all accessories; if certain accessories or engine-driven equipment cannot be shut down, set them to minimize engine load For manual transmissions, shift into "Neutral," and for automatic transmissions, place the gear in the "Park" position to guarantee safety during maintenance or servicing.
“Park” Smoke instrumentation shall be installed and calibrated in accordance with the provisions of 7.3 and clause 8
The acceleration test is a procedure that accelerates the engine from low idle speed to high idle speed
The acceleration test involves a specific sequence to ensure engine stability, beginning with stabilizing the engine at low idle speed for 15 seconds ± 5 seconds Next, the speed control lever is moved rapidly to the wide open position and held until the engine reaches its governed high idle (no load) speed Afterward, the lever is returned to the closed position, allowing the engine to return to its low idle speed This sequence is repeated twice as practice runs to clear out the exhaust system Following these practice runs, the sequence is repeated until three consecutive runs meet the specified stability criteria, ensuring reliable engine performance during acceleration testing.
A.3.5.2 Test validation criteria — Acceleration test
The acceleration test results shall be considered valid only after the following test cycle criteria have been met
The maximum 1.0 s Bessel-averaged smoke values obtained from three successive acceleration tests must not differ by more than 5.0% in opacity, ensuring consistent and reliable emissions measurements Additional validation criteria for these tests are outlined in sections 5.1.2 and 7.3.4, providing comprehensive guidelines for test accuracy and compliance.
A.3.5.3 Determination of free acceleration time (FAT)
The free acceleration time for an individual acceleration, as specified in A.3.5.1 e), is the duration from when the engine speed departs from low idle until reaching high idle speed This FAT measurement is essential for comparing actual in-field acceleration times to those used during engine certification or type approval under ISO 8178-9 standards If the in-field acceleration time exceeds nine times the free acceleration time, it indicates a significant discrepancy that may require further evaluation.
ISO 8178-9, then the engine should not necessarily be expected to meet the limit value a High idle b Rated c Idle d Practice runs e Actual runs
(a), (b) and (c) refer to paragraphs in A.3.5.1
This clause outlines the process for analyzing acceleration test results, emphasizing the importance of signal processing in opacimeter measurements Many opacimeters utilized for this test provide a smoke output signal representing an X = 0.5 s Bessel-average smoke, as specified in section 10.2 To obtain more comprehensive data, these devices require additional signal conditioning to generate X = 1.0 s smoke results Proper interpretation of these signals is essential for accurate assessment of emissions during acceleration testing.
(t p 2 + t e 2 ) used in equation (11) in 10.2.2 is 0,5 2 The results of raw smoke analysis, those not already processed according to the 0,5 s Bessel algorithm, shall use a (t p 2 + t e 2 ) value that represents the opacimeter system
Reported smoke values shall also be corrected for ambient conditions as described in 10.3
PSV values should be determined for each acceleration event specified in section A.3.5.1 e), focusing on the maximum X = 1.0 s Bessel-averaged smoke levels It is essential to analyze smoke data that accurately corresponds to the duration of the acceleration event to ensure precise assessment, as outlined in section 10.1.1.