British-Korean youngster Jack Aitken will be the Renault Formula One team’s official reserve driver this season, replacing Russian Sergey Sirotkin, who has switched to a race seat with Williams.The Renault team made the announcement on Tuesday after an online presentation of its new RS18 car.Aitken, 22, will also race in the Formula Two feeder series this season.Renault will continue the Russian connection with Artem Markelov, who is also competing in F2 and has been appointed as a test and development driver with an emphasis on simulator duties at the team’s Enstone factory in England.The French manufacturer finished sixth overall in last year’s championship, up from ninth the previous season, and are aiming to close the gap further after significant investment in staff and facilities.Renault, who have Germany’s Nico Hulkenberg and Spaniard Carlos Sainz as their driver line-up, last won the championship with Spaniard Fernando Alonso in 2006.“We are a team on the rise,” Renault Sport Racing president Jerome Stoll said in a statement. “Enstone is regenerated and the workforce has already increased by more than 35 percent.“I am convinced year three will take us one step closer to the long-term aim: winning races and challenging for championships.”Renault sold their team to Genii Capital in 2010 but bought it back at the end of 2015 when the outfit, renamed Lotus, was close to failure.Cyril Abiteboul, the Renault Sport Racing managing director, said the first year was all about building up the team and brand and securing new sponsors, with last year bringing on-track progress.“We have everything to be positive about this year,” the Frenchman said. “Our headline target is to show continued progression through results. We want to be able to showcase our progression in every regard; power unit, chassis, operations, drivers. Everything must improve and we must continue to grow.”Neither of the Renault drivers have stood on the podium in their careers and Hulkenberg now holds the Formula One record for most career starts (135) without a top-three finish.“We’re in a good position,” said the German, who joined the team last year from Force India. “For this year we want to build on the good platform of last season. 2017 was about bedding in, now I want to get ready to go.”Testing begins at Barcelona’s Circuit de Catalunya on Monday, with the opening race in Australia on March 25.