# Identification of the Parameters of the Szpica–Warakomski Method’s Rectilinear Trend Complementary to the Gaussian Characteristic Area Method in the Functional Evaluation of Gas Injectors

## TL;DR

This paper evaluates a modified diagnostic method for gas injectors to assess their performance under new emission regulations.

## Contribution

The study introduces a modified Szpica–Warakomski rectilinear trend method for evaluating gas injector functionality.

## Key findings

- The modified method showed strong dependence of trend parameters on injector design and operating conditions.
- The directional coefficient was significantly affected by operating conditions, while opening/closing times had no significant impact.
- The method proved useful for evaluating gas injectors of different models and conditions.

## Abstract

The Fit for 55 and Euro 7 regulations significantly reduce CO2 emissions from combustion sources. This will be reflected in the regulations governing the approval of in-service vehicles, including those using alternative fuels. The present study focused on the rapid diagnostics of the technical condition of gas injectors. The test method was a modification of the Gaussian characteristic fields method using the Szpica–Warakomski rectilinear trend. The flow tests resulted in average volumetric intensities of 111 NL/min and 124 NL/min, depending on the operating conditions. The opening and closing times were in the range of (1.3…3.5) ms. The directional parameter of the rectilinear trend, which is important from the point of view of the analyses, was 0.97 for brand new (BN) injectors and 1.00 for in-service (IO) injectors. The intersection parameters were 0.64 and 0.24, respectively. The qualitative evaluation yielded coefficients of determination of 95.01 and 94.07. The values of the trend parameters were strongly dependent on the design solution and model/type of injector. Inferring the effect of operating condition on the trend parameter values, a one-factor analysis of variance was performed, which showed the significance of only the directional coefficient. A comparison of the same BN and IO injector model showed an apparent change in the value of the intercept only. No significant relationships between the injector opening and closing times and the trend parameters were shown. Thus, the usefulness of using the Szpica–Warakomski rectilinear trend in the functional evaluation of gas injectors of different designs and under different operating conditions was demonstrated.