GMW GMW16411 PDF

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose The purpose of this test is to determine the robustness of an intake manifold to withstand the combustion of an internal air and fuel vapor mixture. The document defines all requirements for product validation to a rapid pressurization event.

Foreword.

• Intake Manifold Rapid Pressurization refers to a combustion event internal to the intake manifold which results in an internal pressure greater than ambient.

• Intake Manifold Over Pressurization refers to a combustion event internal to the intake manifold which results in a manifold failure. The failure may be catastrophic, such as a structural failure of the manifold cavity which causes an excessive air leak, or a minor failure, such as a hose or component that becomes dislodged and causes a small air leak.

• Backfire refers to an event during engine operation or engine starting when a combustible mixture of fuel and air in any cylinder is ignited and a flame front propagates into the intake manifold. The intake manifold may or may not contain an ignitable mixture of fuel and air. If the manifold does contain an ignitable mixture of fuel and air, the mixture will burn, creating a rapid pressure rise.

• Rapid Pressurization implies a pressure event duration of 7 to 100 ms. During the transition in material usage for intake manifolds to polyamide composites from aluminum, structural robustness became an issue during an engine backfire. To investigate this, a laboratory bench test was needed to simulate the in-field phenomena. The Intake Manifold Rapid Pressurization Test was developed to closely simulate the conditions that occur in the vehicle.

• Propane is used instead of gasoline since propane mixes easily with air and remains a vapor at normal ambient temperature. The volume specific energy content of gasoline is 3.51 kJ/L versus propane at 3.38 kJ/L.

• The theoretical maximum internal pressure from an internal combustion event is 930 kPa. This may result from the combustion of a stoichiometric mixture of air and gasoline vapor at ambient conditions. This pressure level assumes complete combustion of all air and vapor with no leakage. For this condition to occur, all leak paths, including all intake and exhaust valves, must be closed which is always unlikely, and often impossible, depending on the engine configuration.

• Combustion tests have demonstrated significant differences in peak pressure between manifold designs. This is due to differences in burn characteristics that result from differences in manifold geometry. For this reason, the acceptance criterion is not a single pressure.

Applicability. This procedure applies to intake manifolds for all gasoline fueled, spark ignition engines. It is intended mainly for intake manifolds made from composite materials or other materials and construction methods which may not withstand pressures over 930 kPa internal pressure. It may also be adapted to evaluate induction systems or other vessels that may contain fuel vapor.