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March 07,2021           John Roebuck          Abhinay Kalburgi          Articles

Using Simulation to Reduce the Time and Cost of Meeting Emissions Regulations


The client is a leading Indian manufacturer of engines for use in automotive and off-highway industries.

A Low-Cost Approach to Meeting Emissions

India has been moving toward new emission norms and those proposed for generator sets (CPCB IV+) are amongst the most stringent in the world. With no standard technology approach yet established each OEM has to determine what will be the most efficient package for their product and market. The development and prototyping costs of emissions programs can be prohibitive. This makes it all the more important to get the recipe right the first time to minimise cost and time overruns.

Simulation Benefits versus Testing

A certain amount of prove out can happen on the test bed. However, with options matrices running in several dimensions, this can be an expensive and time-consuming process. 

The Figures show the equivalence ratio distribution for baseline and iteration for equivalent crank-angles

Caepro has simulation tools and techniques for developing the engine virtually. As well as being relatively quick, simulation can also improve understanding about why a particular solution is or isn’t working.This is more difficult to achieve in physical testing. Performing tests virtually also reduces the number of components that need to be purchased for testing which can be very expensive.

Emissions Strategy

The client wanted to meet the emissions regulations without having to resort to using a DPF which would increase the cost of the engine and result in additional service issues such as blocking and regeneration. They, therefore, wanted to focus on minimizing in-cylinder soot generation.This strategy was likely to lead to an increase in NOx but there was some margin for this.It was decided that for any new hardware which was already available it would be easier to do physical verification through testing.Wherever hardware availability was an issue, or it was difficult to change the parameters, it was decided that simulation would be performed.

Baseline Correlation

A “virtual twin” using both 1D and 3D CFD was generated and calibrated to the client’s test results. The robustness of the model was then established by comparing emissions predictions with test at different injection timings. Good correlation was achieved with NOx within 5% of test data at each of the 5 load test conditions and soot within 10%. This established confidence within the client’s team that simulation results could provide useful indicators for emissions performance in further iterations.

Emissions Simulation

With changed hardware including nozzle tip projection and turbocharger initial soot reduction of about 40% was achieved on the test bed and this was matched in the  simulation results. This further increased confidence in the virtual model.The virtual model was then used to vary additional parameters to optimise the emissions performance. Piston bowl shape, injection pressure, number of injector holes and nozzle tip protrusion were changed. An additional 8% reduction in soot was achieved.

The figures show the equivalence ratio distribution along the radius of the cylinder.

With increase in number of sprays reduction in equivalence ratio is observed

Objectives Achieved

Careful selection of optimisation parameters kept the negative impact on NOx emissions low enough to have a negligible impact on ATS loading.The emissions norms were achieved with only DOC+SCR i.e. no requirement of DPF. The achievement was done with minimal design and component changes.

The baseline calibration was very accurate and subsequent iterations have been helpful in giving us directional indicators and reducing development time.I am very happy with the project and would engage Caepro for further support for other emission norms. I would highly recommend any engineering company to conduct a similar exercise with Caepro“. Head R&D, Indian Engine OEM.

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