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Opti­mised inter­ac­tion

How a fan, venturi and gas valve form a perfect system

The NRV 77 is a system for gas condensing boilers consisting of the NRG 77 blower, an inno­v­a­tive multi-venturi and E 01 gas valve. In order to co-ordi­nate these single compo­nents opti­mally with one another, we had to over­come three major hurdles.

Typical CO2 curve and Venturi pilot pres­sure curve

The fan covers a power range from 1 to 35 kilo­watts. It is oper­ated at speeds up to 11,500 revo­lu­tions per minute, yet is signif­i­cantly smaller than its prede­ces­sors. We are working with a smaller impeller diam­eter in order to satisfy the require­ment of our customers for ever smaller heat outputs. This also presents new chal­lenges for the bearing tech­nology, since the fric­tion torques gain greater signif­i­cance. There­fore, it was impor­tant to guar­antee the correct balance between viscosity of the grease and the service life of the fan. We safe­guarded this by means of numerous endurance and devel­op­ment tests.

EA constant fuel-air mixture across the entire oper­ating range is highly signif­i­cant for the func­tion of the gas condensing boilers. NRV systems have a large modu­la­tion range from one to seven, over which the air-fuel ratio of the combus­tion has to be controlled. What is called the main injec­tion throttle of the gas valve is an impor­tant element here. It is used to configure the desired gas volume flow at full load. It consists of a rotating plastic part, which is fastened in place on a sheet.

The parts have to be flushed with one another to ensure that the entire gas quan­tity is fed through the main injec­tion throttle and no leaks past the throttle can develop. These leaks would have a nega­tive impact on the smallest attain­able partial load of the gas condensing boiler. And this partial load – as many customers require – should be as small as possible. In order to fit the plastic part to the sheet metal better, we temper it. We were also able to further opti­mise the sheet metal part since we have long-time expe­ri­ence with punches in the Produc­tion depart­ment in Land­shut, Germany. Thus we were able to achieve the goal of creating a largely leakproof main injec­tion throttle that can be moved ideally.

NRV 77 with multi-venturi and gas valve

A single venturi cannot cover the large power range of the fan. However, we wanted to find an easy and cost-effec­tive solu­tion for adapting the venturi to the power range desired by the customer. To do so, we created a venturi with an inte­grated displace­ment body. The displace­ment body forms the actual venturi diam­eter. This diam­eter can be easily modi­fied, yet it does not worsen the perfor­mance. Addi­tion­ally, the entire venturi can be flex­ibly attached to the fan in many different mounting posi­tions. This brings flex­i­bility to the customer and fewer design vari­a­tions for us. We have had this solu­tion patented and call it “multi-venturi”.

The system solu­tion consisting of blower, venturi and valve makes co-ordi­na­tion easier for devel­opers of gas-fired heaters. Addi­tion­ally, the perfect inter­ac­tion of the indi­vidual compo­nents improves effi­ciency and reduces costs.

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  • zhou maozhen on said:

    Where can i buy it?

    • klindner on said:

      Dear Zhou,

      Thank you for your request – We have forwarded it our sales team.

      Best regards,
      Your mag°-Team