An Electrohydraulic Gas Sampling Valve with Application to Hydrocarbon Emissions Studies

Design and development of an electrohydraulically actuated gas sampling valve is presented for use in auto engine combustion studies. The valve was developed with particular emphasis on sampling within the vicinity of the wall quench layer, requiring minimum leakage rates to avoid sample contamination and flush seating of the valve-stem to valve-seat to avoid perturbations of the wall layer. Response in the range of 0.4 to 1.0 milliseconds is attainable for variable valve lifts measured between 0.01 to 0.30 mm while using a net sealing force of approximately 750N. Gas leakage rates ranged from 0.05% to 1% of the sample mass flow rate when sampling from estimated distances from the wall of 0.3 mm to 0.03 mm, respectively, at a cylinder pressure of 10 bar.

The gas sampling valve is presently coupled to a gas chromatograph to measure concentrations of major species components. Initial studies have focussed upon determining species profiles near the wall at specific times after flame arrival at one sampling location in the engine cylinder. The results indicate that the contribution of wall quench layer hydrocarbons to the engine exhaust is substantially smaller than previously estimated.